In recent years, in order to increase a data storage capacity, an optical recording medium, especially a blue-ray disc, has been developed and practically used that converges a laser beam with a wavelength of 405 nm using an objective lend having a numerical aperture of 0.85 so that data is stored.
Such an optical recording medium has a support substrate having a thickness of 1.1 mm on which at least a recording layer and a light transmission layer that transmits a laser beam having a thickness of about 100 μm are laminated.
Thus, the support substrate and the light transmission layer have different thicknesses, and are generally made of materials having different physical properties such as elastic modulus. Therefore, the optical recording medium is undesirably easily warped by a change of an ambient temperature etc.
Japanese Patent Application Laid-open No. 2008-071439 proposes that a light transmission layer is formed by a photo-curable resin having a specific storage elastic modulus at 25° C. in order to prevent degradation of mechanical properties, especially a radial tilt properties, of the optical recording medium even when the optical recording medium is stored for prolonged period.
Japanese Patent Application Laid-open No. 2009-026379 proposes that a write-once type optical recording medium has a light transmission layer having a storage elastic modulus at 5° C. of 100 MPa or less and a storage elastic modulus at 55° C. of 100 MPa or less and having a ratio of the storage elastic modulus at 5° C. and the storage elastic modulus at 55° C. of 10 or less; and a recording layer formed by an organic dye in order to prevent a decrease in record and reproduction properties even when the optical recording medium is stored for prolonged period.